From 95b10ec3ef02c30505eda3914810ea37038cd7d8 Mon Sep 17 00:00:00 2001
From: Donovan Glover <donovan@dglover.co>
Date: Tue, 2 Apr 2024 05:15:15 -0400
Subject: [PATCH] meta: Begin writing tests in Nix
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Now that I've figured out how to dynamically import modules and use
those modules as outputs, the next step is to ensure that these modules
work as intended when being used by end users.

NixOS offers a built-in testing solution that enables us to conveniently
spin up virtual machines with a given configuration, then verify their
correctness through python scripting.

The lib.nix file in particular is based on Jörg Thalheim's very useful
blog post that explains how to use the built-in testing functionality
with Nix flakes, which isn't covered in official documentation.

See: https://blog.thalheim.io/2023/01/08/how-to-use-nixos-testing-framework-with-flakes/
---
 flake.nix          | 10 ++++++++++
 tests/hyprland.nix | 15 +++++++++++++++
 tests/lib.nix      | 13 +++++++++++++
 tests/neovim.nix   | 15 +++++++++++++++
 4 files changed, 53 insertions(+)
 create mode 100644 tests/hyprland.nix
 create mode 100644 tests/lib.nix
 create mode 100644 tests/neovim.nix

diff --git a/flake.nix b/flake.nix
index 27e3a63e..37bc7590 100644
--- a/flake.nix
+++ b/flake.nix
@@ -25,6 +25,11 @@
     inherit (nixpkgs.lib) nixosSystem;
     inherit (nixpkgs.legacyPackages.x86_64-linux) nixpkgs-fmt callPackage;
 
+    checkArgs = {
+      pkgs = nixpkgs.legacyPackages.x86_64-linux;
+      inherit self;
+    };
+
     flakeOutputs     =  [ "overlays" "nixosModules" "homeManagerModules" "packages" ];
     flakeDirectories =  [ "overlays" "modules"      "home"               "packages" ];
     packageDirectory = "packages";
@@ -55,6 +60,11 @@
         ];
       };
     };
+
+    checks.x86_64-linux = {
+      hyprland = import ./tests/hyprland.nix checkArgs;
+      neovim = import ./tests/neovim.nix checkArgs;
+    };
   } //
     (builtins.listToAttrs
       (builtins.map
diff --git a/tests/hyprland.nix b/tests/hyprland.nix
new file mode 100644
index 00000000..64f0795f
--- /dev/null
+++ b/tests/hyprland.nix
@@ -0,0 +1,15 @@
+# TODO: Write test to ensure that Hyprland starts with basic config
+(import ./lib.nix) {
+  name = "hyprland";
+
+  nodes.machine = { self, pkgs, ... }: {
+    imports = with self.nixosModules; [
+      hyprland
+    ];
+  };
+
+  testScript = /* python */ ''
+    output = machine.succeed("echo 'Hello world'")
+    assert "Hello world" in output
+  '';
+}
diff --git a/tests/lib.nix b/tests/lib.nix
new file mode 100644
index 00000000..93748faa
--- /dev/null
+++ b/tests/lib.nix
@@ -0,0 +1,13 @@
+test: { pkgs, self }:
+let
+  inherit (pkgs) lib;
+  nixos-lib = import (pkgs.path + "/nixos/lib") { };
+in
+(nixos-lib.runTest {
+  hostPkgs = pkgs;
+  defaults.documentation.enable = lib.mkDefault false;
+  node.specialArgs = {
+    inherit self;
+  };
+  imports = [ test ];
+}).config.result
diff --git a/tests/neovim.nix b/tests/neovim.nix
new file mode 100644
index 00000000..ed0d0aa4
--- /dev/null
+++ b/tests/neovim.nix
@@ -0,0 +1,15 @@
+# TODO: Ensure that neovim config works without errors on startup
+(import ./lib.nix) {
+  name = "neovim";
+
+  nodes.machine = { self, pkgs, ... }: {
+    imports = with self.nixosModules; [
+      neovim
+    ];
+  };
+
+  testScript = /* python */ ''
+    output = machine.succeed("echo 'Hello world'")
+    assert "Hello world" in output
+  '';
+}